Exposure to toxic chemical and biological agents (“CBAs”) is a growing concern to both military and civilian organizations alike. Areas of enhanced vulnerability include assemblies of persons, whether military or civilian. One such scenario includes military personnel assembled within one or more tents and/or portable shelters.
In order to mitigate the harmful effects of an exposure to CBA agents, many military shelters are constructed from fabrics which include one or more polymeric materials exhibiting barrier properties to one or more toxic agents. Many of these fabrics comprise, for example, fluoropolymers such a polytetrafluoroethylene (“PTFE”). One such composite material comprises Teflon coated Kevlar. While such composites demonstrate acceptable barrier properties, these CBA barrier shelter fabrics are expensive and require multiple manufacturing operations to join various fabric segments. The high costs of materials in combination with high manufacturing costs limit the availability of such prior art fabrics for widespread use.
As a result, most real-world military shelters are not made from such fabrics. Rather, current shelters are formed using materials having inferior CBA resistance. For example, forces of the United States of America typically utilize a General Purpose Shelter Fabric (“GP Fabric”) manufactured from cloth coated with polyvinyl chloride (“PVC”). GP Fabric is relatively inexpensive and affords soldiers adequate protection against inclement weather including rain, snow, wind, and dust storms. Shelters made from GP Fabric, however, offer minimal CBA protection. Such prior art shelters require an additional M28 Saranex liner to impart acceptable CBA barrier properties. As those skilled in the art will appreciate, use of such liners adds to the overall weight, cost, and complexity, of the shelter.
Applicant's invention includes a more convenient, lower cost means of providing CBA resistance comprising disposing a waterborne CBA barrier coating directly onto either the interior, exterior, or both, of shelters made from GP Fabric. Applicant's method uses conventional coating methods, such as knife coating, spray coating, calendaring, and the like. Waterborne coatings are desirable because of inherent low toxicity and low flammability properties. Applicant's coating solutions rapidly and uniformly spread over the shelter surfaces, including the seams, thereby producing a continuous CBA barrier film after drying. Applicant's coating effectively “hardens” the shelter, i.e. enhances its CBA barrier properties.
As those skilled in the art will appreciate, in order for any barrier coating to be effectively repel toxic agents, that coating must exhibit a high degree of mechanical integrity. In addition, that coating must adhere well to the GP Fabric substrate such that the coating neither tears nor delaminates from the fabric. Poor mechanical strength and/or poor adhesion greatly increase the likelihood of forming cracks and other coating defects that facilitate passage of toxic chemicals into the shelter.